The present invention relates to disc drive data storage systems. More particularly, the present invention relates to multi-actuator disc drives.
Disc drive data storage systems use rigid discs which are coated with a magnetizable medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted in a stack on the hub structure of a "brushless" direct current spindle motor which causes the discs to spin and the surfaces of the discs to pass under respective hydrodynamic (e.g. air) bearing disc head sliders. The sliders carry transducers which write information to and read information from the disc surfaces. Each slider is supported by an actuator arm and a suspension. Each actuator arm is supported by a common actuator body, which is often referred to as an "E-block". The E-block supports each actuator arm and its suspension relative to a respective one of the disc surfaces. An electromechanical actuator, such as a rotary moving coil actuator or "voice coil motor," operates within a negative feedback, closed-loop servo system to rotate the E-block and thus move the actuator arms together radially over the disc surfaces for track seek operations and hold the read/write heads directly over a track or common cylinder on the disc surfaces for track following operations. Conventional disc drives have only one read/write channel and therefor can only read or write with one head at a time.
Disc drives having multiple voice coil motors for independently rotating multiple E-blocks are known in the art. Such disc drives allow one or more voice coil motors to position their read/write heads at other tracks while another read/write head is reading or writing. Also, in a system which employs multiple read/write channels, two or more independent read/write heads can simultaneously read or write at different radial positions of the disc stack. One drawback of these existing multiple actuator systems is that they use a totally independent servo loop to control each voice coil motor. Furthermore, existing systems require one set of state machines and look-up tables for each voice coil motor in order to control the independent voice coil motors. Thus, the requirement in existing systems of multiple voice coil motor controllers and multiple sets of memory for the state machines and look-up tables results in increased cost, increased weight, increased volume and increased complexity.
The present invention addresses these and other problems, and offers other advantages over the prior art.